docs: adjust sdk page to show/hide messages based on whether online or offline docs

</script>

  <?cs else ?> <?cs # end if online ?>

    <?cs if:sdk.preview ?>

    <?cs if:sdk.preview ?><?cs # it's preview offline docs ?>

      <p>Welcome developers! We are pleased to provide you with a preview SDK for the upcoming

    Android 3.0 release, to give you a head-start on developing applications for it.

    </p>

    <style type="text/css">

    .non-preview { display:none; }

    </style>

    <?cs else ?><?cs # it's normal offline docs ?>

      <style type="text/css">

        p.offline-message { display:block; }

        p.online-message { display:none; }

      </style>

    <?cs /if ?>

  <?cs /if ?> <?cs # end if/else online ?>

<?cs /if ?> <?cs # end if/else NDK ?>